Throttle angle transducers

ABSTRACT

A throttle angle transducer having a non-linear output which changes more rapidly at small throttle angles than at large throttle angles, comprises a linear potentiometer operated by the throttle pedal, and an oscillator having a period which is determined by the potentiometer output and which varies linearly from the throttle angle. The frequency of the oscillator is employed to provide the required output from a transducer.

United States Patent Ironside et a].

THROTTLE ANGLE TRANSDUCERS Inventors:

Assignee:

Filed:

Appl. No.:

John Michael lronside, Birmingham; Michael Herbert Cops, Solihull, bothof England Lucas Electrical Company Limited, Birmingham, England Feb.13, 1973 Foreign Application Priority Data Feb. 25. 1972 US. CL... int.CL

United Kingdom 8937/72 123/32 EA; 123/119 R Field of Search 123/119 R,132 EA References Cited UNITED STATES PATENTS TRANSDUCER Aono et al123/32 EA MEMORY i i DEl/ICE 51 Sept. 30, 1975 3,703,162 11/1972 Aono123/32 EA 3.719.176 3/1973 Shinoda et al. 123/32 EA 1765.380 10/1973Rachel et al. 123/32 EA 3,786,788 1/1974 Suda et al 123/32 EA PrimaryE.\'aminer-Charles J. Myhre Assistant Examiner-Joseph A. C angelosiAttorney, Agent, or Firm-Holman & Stern [57] ABSTRACT 1 Claim, 4 DrawingFigures FUEL INJECTION CO NTROL w '5 OSCILLATORS ,is ,e

idem NETWORK LATCHING COUNTER -COUNTER LOGIC =:?TNETW0RK F? El US.Patent Sept. 30,1975 3,908,614

MEMORY FUEL \NJECTION TRANSDUCER DEVICE CONTROL IE IS T LATGHING COUNTERCOUNTER mm W QWETWoRK 0SClLLAT0RS I7 g /l 9 E NETWORK PERIOD Flea.

THROTTLE ANGLE EFFECTIVE FREQUENCY FREQUENCY THEGTTLE ANGLE- THEOTTLEANGLE FTC-3.3. FIGA.

THROTTLE ANGLE TRANSDUCERS This invention relates to throttle angletransducers for use in fuel injection systems.

In order to attain satisfactory accuracy in a fuel injection system, itis desirable to employ a throttle angle transducer having a non-linearoutput which changes more rapidly at small throttle angles than at largethrottle angles, because at small throttle angles the rate of change offlow of air when the pedal is moved is substantially higher than atlarge throttle angles. The desired output can be obtained by employing anonlinear potentiometer, but such potentiometers are expensive anddifficult to manufacture to the required degree of accuracy.

The invention resides in a throttle angle transducer having a non-linearoutput which changes more rapidly at small throttle angles than at largethrottle angles, comprising a linear potentiometer operated by thethrottle pedal, and an oscillator having a period which is determined bythe potentiometer output and varies linearly with the position of thethrottle pedal, and the frequency of the oscillator being employed toprovide the required output from the transducer.

Preferably, the frequency is measured digitally by using a countingdevice to count to a value representing the frequency at any giveninstant, and in this case the shape of the frequency against throttleangle curve can be changed to suit any particular application bysubtracting a fixed digital number from each digital count.

The invention further resides in a fuel injection system for a vehicle,including a throttle angle transducer as specified above, a secondtransducer for measuring a further engine parameter, and a memory deviceto which the outputs from the transducers are fed, the memory devicedetermining the quantity of fuel injected in accordance with the valuesof the two parameters.

An example of the invention is illustrated in the accompanying drawings,in which:

FIG. 1 is a block diagram, and

FIGS. 2 to 4 are graphs illustrating roughly wave forms pertinent to theexample.

Referring first to FIG. 1, there is provided a memory device 11 whichreceives an electrical input from a transducer 12 representing eitherengine speed or manifold depression, and receives a further electricalinput from a latching counter 13 in a manner to be described, the inputfrom the counter 13 to the memory device 11 representing throttle angle.The memory device 1 1 produces an output, the value of which isdependent on the values of the two input signals it receives, and thisoutput is used to operate means 14 for controlling the injection of fuelto the engine ofa road vehicle. The exact nature of the memory device 11is not important for an understanding of the present invention.

In order to obtain a signal representing a throttle angle, there isprovided a potentiometer 15 which produces a linear output, that is tosay a voltage which varies linearly with throttle angle. The signalobtained from the slider of the potentionmeter 15 is fed to afreerunning square wave oscillator 16 of any convenient form, thearrangement being such that the signal received by the oscillator 16from the potentiometer l5 varies the period of the oscillator, so thatthe period of the oscillator varies with throttle angle in a linearmanner as indicated in FIG. 2. It will be appreciated that since thefrequency of an oscillator is inversely proportional to its period, thenthe frequency of the oscillator 16 will vary with throttle angle in themanner shown in FIG. 3.

The output from the oscillator 16 is fed to a counter 17 which passes asignal to the counter 13 from time to time in a manner to be explained.The circuit also includes a fixed frequency oscillator 18 which has aperiod substantially in excess of the period of the oscillator 16. Inone particular example, the period of the oscillator 18 is equal to thetime taken for the oscillator 16 to produce 32 pulses, even when theoscillator 16 is operating at its minimum frequency. The output from theoscillator 18 is fed to a logic network 19, and at the commencement of aperiod of oscillation of the oscillator 18, the logic network producesone output pulse which is applied to the counter 13 so that the counter13 is fed with the information which at that moment is present in thecounter 17. The counter 13 then retains this information until thebeginning of the next period of the oscillator 18. Moreover, at thecommencement of the period of the oscillator 18, the logic network 19produces a further pulse which clears the counter 17, which then startsto receive a count from the oscillator 16. After the counter 17 hasreceived 32 pulses, a further logic network 21 clears the counter 17again, but the counter 17 then starts filling again by virtue of furtherpulses received from the counter 16. Thus, it will be seen that at theend of a period of the oscillator 18, when the reading of the counter 17will be passed onto the counter 13, the reading in the counter 17 willrepresent the number of pulses received from the oscillator 16 duringthe fixed period of the oscillator 18, less 32 pulses by virtue of thelogic network 21. The effect of subtracting these 32 pulses from thereading of the counter 17 is that the graph shown in FIG. 3 effectivelybecomes of the form shown in FIG. 4. It will be seen that this graph isof the form required, in that the effective frequency shown in FIG. 4,that is to say the frequency after allowance is made for the 32subtracted pulses, varies with throttle angle in such a manner that atsmall throttle angles the signal received by the counter 13 will changemore rapidly than at large throttle angles.

We claim:

1. A throttle angle transducer which can be used in a fuel injectionsystem for a vehicle having a throttle pedal, and which has a nonlinearoutput which changes more rapidly at small throttle angles than at largethrottle angles, said transducer comprising in combination a linearpotentiometer having movable thereon a slider which is driven by thethrottle pedal which determines said throttle angle, an oscillator,means coupling said oscillator to said slider, said potentiometerdetermining the period of said oscillator, whereby said period varieslinearly with the position of said slider, and an output stage coupledto said oscillator, said output stage providing an output signal whichvaries linearly with the frequency of the oscillator, the frequency ofsaid oscillator being determined solely by its period, said output stageeffecting digital measurement of said oscillator frequency and includingmeans comprising a digital counting device for counting to a valuerepresenting the oscillator frequency at any given instance, the shapeof the frequency against the throttle angle curve being determined bythe output of means for subtracting a fixed digital number from eachdigital count.

. UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO.3,908,614

' DATE I September 30, 1975 INVENT0R(5) I John M. Ironside, et a1 It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

[30] Forelgn PIlOIltY Data:

Great Britain No. 8925/72 filed February 25, 1972 Signed and Scaled thisthir Day Of January 1976 [SEAL] Attest:

RUTH c. MASON C. MARSHALL DANN Arresting ffic Commissioner ufPatenls andTrademarks

1. A throttle angle transducer which can be used in a fuel injectionsystem for a vehicle having a throttle pedal, and which has a nonlinearoutput which changes more rapidly at small throttle angles than at largethrottle angles, said transducer comprising in combination a linearpotentiometer having movable thereon a slider which is driven by thethrottle pedal which determines said throttle angle, an oscillator,means coupling said oscillator to said slider, said potentiometerdetermining the period of said oscillator, whereby said period varieslinearly with the position of said slider, and an output stage coupledto said oscillator, said output stage providing an output signal whichvaries linearly with the frequency of the oscillator, the frequency ofsaid oscillator being determined solely by its period, said output stageeffecting digital measurement of said oscillator frequency and includingmeans comprising a digital counting device for counting to a valuerepresenting the oscillator frequency at any given instance, the shapeof the frequency against the throttle angle curve being determined bythe output of means for subtracting a fixed digital number from Eachdigital count.